This application is a formative step towards assessing dietary intake of N-Nitroso compounds in populations to inform subsequent epidemiological investigations and dietary methodology. Lung, stomach, upper gastro-intestinal tract, pancreatic, colorectal, and brain cancers are leading causes of cancer morbidity and death. Mutagenic/carcinogenic N-nitroso compounds in foods have been described in the etiology of these cancers. In order to make a major impact on these cancers, a better understanding of novel dietary preventive strategies is essential. For example processed and preserved meats have a positive association with increased risk of cancer. However, investigations pursing estimates of N-nitroso intakes have been impeded by the lack of a database that summarized N-nitroso food values, and the food patterns driving their intake is unknown across the US population, among subgroups who are at risk for cancer. Lack of such knowledge is an important problem, because, without it, we are unable to fully identify the carcinogenic role of dietary N-nitroso compounds and to make public health recommendations to reduce their intake. To fulfill the gap, we recently developed a dietary database of N-nitroso compounds. The current project will take advantage of the existing N-Nitroso database and the National Health and Nutrition Examination Survey (NHANES) 2003-2004 to validate and measure N-Nitroso compound intake in the total population and by subgroups (race/ethnicity, age group, BMI, income, and leisure activity). We will further explore the interaction of N-nitroso compounds and antioxidants, and the major food contributors of N-nitroso compounds according to population subgroups. The central hypothesis is that high dietary intake of N- Nitroso compounds alone and in interaction with other nutrients vary by subgroups. Using NHANES 2003-2004 dietary, demographic, and other variables in 5280 adults, our existing database of N-nitroso compound values will be linked to foods reported in two 24-hour dietary recalls per sample person. The main effects of the variables and their interactions will be examined by using the new NCI Method of estimating dietary intakes of compounds and foods with programs adapted for NHANES datasets. The proposed study is innovative because it will result in adapting dietary methodology for N-nitroso estimates, and combine existing resources of a N-nitroso dietary database, together with the dietary, demographic, and clinical data from a large national dataset. Information gathered from this study will be valuable in generating novel dietary related hypotheses for cancer case-control studies, and to identify foods and questions for improving dietary methodology specific for N-Nitroso assessment.